Stafford posted a message to his Twitter account Thursday indicating he felt good throwing in Athens, Ga., two months after having surgery on his right shoulder.
Stafford tweeted that he was heading to "rehab, lift and run" during the NFL lockout. He added: "Never know when the owners will let us back in to start playing."
Stafford said Tuesday at University of Georgia pro day -- he attended the school before going No. 1 overall in the 2009 NFL Draft -- that he is recovering well and rehabilitating in Birmingham, Ala., with therapists from Dr. James Andrews' office. Andrews performed the surgery on Stafford's right shoulder in January.
Stafford played in just three games last season. He played in 10 games as a rookie.
The Lions can receive reports on Stafford's progress, but they aren't permitting to make contact with him during the lockout.
"There's nothing he's had injury-wise his first two years that is going to affect him going forward," Schwartz added. "He knows that, we all know that. We (just) need to keep him on the field."
The Associated Press contributed to this report.